STRUCTURALS
CD5515-2/YB5515-2 SERVICE MANUAL
11-12
Published 1-20-2017, Control# 483-02
WIRE ROPE, SHEAVES AND HOIST
BLOCKS
Wire Rope Description
A wire rope is a machine, by definition: “An assemblage of
parts that transmit forces, motion and energy from one to
another in some predetermined manner and to some desired
end.”
A typical wire rope may contain dozens, even hundreds, of
individual wires which are formed and fabricated to operate
at close bearing tolerances one to another. When a wire rope
bends, each of its many wires slide and adjust in the bend to
accommodate the differences in length between the inside
and the outside of the bend. The sharper the bend, the
greater the movement.
Every wire rope has three basic components (Figure 11-3):
(1) The wires which form the strands and collectively provide
rope strength; (2) the strands, which are laid helical around
the core, and (3) the core, which forms a foundation for the
strands. The core used in the crane wire rope is an
Independent Wire Rope Core (IWRC), which is actually a
smaller rope, or a strand similar to the outer strands of the
rope. The IWRC core adds about 7.5% to the nominal
strength of the wire rope.
The greatest differences in wire ropes are found in the
strands, which may vary widely in the pattern and number of
wires which are laid together.
The wires of the rope may be made of various metals,
including steel, iron, stainless steel, monel, and bronze. The
m a t e r i a l s o f w h i c h w i r e s a r e m a d e i s t h e p r i m a r y
determination of rope strength. High-carbon steel is used in
the crane wire rope.
Carbon steel wire ropes come in various grades. The term
“Grade” is used to designate the nominal strength of the wire
rope. The most common grades are Traction Steel (TS),
Plow Steel (PS), Improved Plow Steel (IPS), Extra Improved
Plow Steel (EIPS) and Extra Extra Improved Plow Steel
(EEIPS). The wire rope used on this crane is an EIPS Grade.
One cannot determine the grade of wire rope by its feel or
appearance. To be sure you are using the proper rope,
always obtain the wire rope from your distributor.
Wire Rope Safety
The following information is not a complete discussion of
wire rope. What follows is a brief outline of the basic
information required to safely use wire rope.
1.
Wire rope WILL FAIL IF WORN-OUT, OVERLOADED,
MISUSED, DAMAGED or IMPROPERLY MAINTAINED.
2.
In service, wire rope looses strength and work capability.
Abuse and misuse increases the rate of loss.
3.
The NOMINAL STRENGTH, sometimes called
CATALOG strength, of a wire rope applies ONLY to a
NEW, UNUSED rope.
4.
The Nominal Strength of a wire rope SHOULD BE
CONSIDERED the straight line pull which will
ACTUALLY BREAK a NEW UNUSED rope. The
Nominal Strength of a wire rope SHOULD NEVER BE
USED AS ITS WORKING LOAD.
5.
WIRE ROPES WEAR OUT. The strength of a wire rope
begins to decrease when the rope is put to use and
continues to decrease with each use.
6.
NEVER OVERLOAD A WIRE ROPE. This means
NEVER use the wire rope where the load applied to it is
greater than the working load determined by the rope
manufacturer.
7.
NEVER “SHOCK LOAD” a wire rope. A sudden
application of force or load can cause both visible
external and internal damage. There is no practical way
to estimate the force applied by shock loading a rope.
The sudden release of a load can also damage a wire
rope.
8.
Lubricant is applied to the wires and strands of a wire
rope when it is manufactured. The lubricant is depleted
when the rope is in service and should be replaced
periodically. See Preventative Maintenance, for
lubrication intervals and procedures.
Wire Rope
FIGURE 11-3
a0358
Reference Only
